摘要:

Measurements of primary productivity can improve assessment of the fish yields from tropical lakes. In tropical African and Indian lakes commercial fish yields increase logarithmically as primary productivity increases arithmetically. The regression equation describing the relation between fish yields (FY) and gross photosynthesis (PG) for eight African lakes is log FY = 0.113 PG + 0.91. The coefficient of determination is 0.57. The regression equation based on fifteen tropical Indian lakes, log FY = 0.122 PG + 0.95, corroborates the relation for Africa.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1976)105<575:PPAFYI>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1976

数据来源: Taylor

摘要:

A costly Simrad acoustical system, calibrated against fish biomass in a keep-net, yielded internally consistent estimates of pelagic ichthyomass in Lake Tanganyika (East Africa). An inexpensive sounder (Furuno), tested alongside the Simrad system, provided information which correlated reasonably well with data from the Simrad system. I did not rigorously demonstrate accuracy of either system. Indices of abundance for the inexpensive sounder, based on depth of fish layers or schools, echogram trace area, and a subjective estimate of trace density correlated sufficiently well with commercial ring-net catches that I could predict fishing success. The indices of fish abundance served also for studies of gross changes in fish distribution.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1976)105<581:AEOPII>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1976

数据来源: Taylor

摘要:

Captive kawakawa, Euthynnus affinis, were instrumentally conditioned to respond to an increase in temperature to determine discrimination abilities. Two fish yielded a discrimination threshold of 0.10 to 0.15 C. Thermal sensitivity of this high-seas pelagic fish is thus no more acute than that of inshore fishes and appears inadequate for direct sensing of weak horizontal temperature gradients at sea.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1976)105<588:TDBCFT>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1976

数据来源: Taylor

摘要:

Age class I and II winter flounder, Pseudopleuronectes americanus, were fed the polychaete, Nereis virens, under experimental temperatures of 10 C and 20 C in a filtered (10 μ), temperature-regulated seawater system for periods of 40 days. All the fish grew and there was no significant difference in growth between fish at 10 C and those at 20 C, but growth was significantly different (P < 0.05) between age classes at both temperatures. Age I fish had the higher growth efficiency and mean gross growth efficiencies based on calories were 23.7% and 20.2% for age I and II, respectively. Calculated efficiencies were lowest based on wet weight and generally increased when based on dry weight, carbon, and caloric content.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1976)105<592:EOWFPA>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1976

数据来源: Taylor

摘要:

The hematology of adult winter flounder was investigated weekly from December 1972 through January 1974. The following parameters revealed statistically demonstrable variation between seasons: hemoglobin (Hb), blood oxygen capacity (CBO2), hematocrit (Hct), red blood cell number (RBC), immature red blood cell number, mean corpuscular volume, mean corpuscular hemoglobin, leukocytes, lymphocytes, thrombocytes, neutrophils, condition factor, and apparent health. The blood constituents concerned with metabolic processes such as oxygen transport, e.g., Hb, Hct, CBO2, and RBC, were lowest during late winter and early spring when winter flounder fast and undergo reproduction activity. At this time the constituents of the blood associated with stress response and infections, i.e., the total white blood cells, were at their yearly peak. The leukocyte count declined during the summer and remained low throughout the rest of the year. Conversely, the Hct, HB, CBO2, and RBC increased during the summer and remained high for the rest of the year. The variation in blood constituents may be in response to the stresses of fasting and spawning during the winter and the alleviation of stressing environmental conditions in the spring.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1976)105<596:SHCIWF>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1976

数据来源: Taylor

摘要:

This study evaluated the physiological response of rainbow trout to hooking stress after being played under standardized conditions (0–5 min) and estimated the time needed for recovery (to 72 h). Plasma osmolality and chloride measurements were used to evaluate osmoregulatory disturbances and gill ion-exchange function, and plasma glucose was used as an index of the generalized nonspecific physiological stress response. Hooking stress caused more severe blood chemistry differences in hatchery fish than in wild trout. Also, hooking stress imposed a greater stress on larger than on smaller hatchery rainbow trout. Higher water temperatures aggravated the delayed hyperglycemia and hyperchloremia in both hatchery and wild trout but only about 3 days were needed for recovery at 4, 10, or 20 C.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1976)105<601:PRTHSI>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1976

数据来源: Taylor

摘要:

Insects, large zooplankton, and some fishes were the main diet of coho salmon (Oncorhynchus kisutch) stocked in Pallette Lake, Wisconsin. From May to early July, coho (117–210 mm total length) were found inshore and in the epilimnion offshore and ate mostly winged flies, ants, and beetles. In late July and August they were primarily captured in the metalimnion and selected some underyearling cisco (Coregonus artedii) and numerous large, rare zooplankton. The latter included Chaoborus punctipennis larvae and pupae, Leptodora kindtii, and Holopedium gibberum. Coho were captured mainly inshore in November and consumed some underyearling cisco and adult hemipterans.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1976)105<607:FHAPSO>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1976

数据来源: Taylor

摘要:

The Sunapee trout (Salvelinus alpinus L.) of Floods Pond, Maine, spawned in October and November when surface water temperatures dropped below 15 C. There was little sexual dimorphism. Sexes were present on the spawning area in nearly equal numbers. Spawning occurred at night in shallow (30 to 100 cm) water near the lake shore. Eggs were scattered over a boulder-strewn bottom. There was neither redd construction nor site preparation. The eggs were relatively large (5.08 mm) and negatively buoyant. Females had approximately 2,500 eggs/kg of body weight. In hatchery tests eggs eyed in about 50 days and hatched in 79–122 days at mean water temperatures ranging from 11.0–3.0 C. The yolk sac was absorbed in about two weeks and the fry immediately moved to deep water. All males were mature at age III+ and all females were mature at age IV+. Many females spawned in alternate years while most males spawned every year.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1976)105<615:RBAELH>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1976

数据来源: Taylor

摘要:

Genetic variation in chinook salmon (Oncorhynchus tshawytscha) from ten hatcheries along the Columbia River drainage and the Oregon coast was described from results of starch gel electrophoresis. Highly significant differences were found between spring and fall chinook in the Columbia River watershed. It was suggested that frequencies of malate dehydrogenase, tetrazolium oxidase, and phosphoglucomutase phenotypes may be influenced directly or indirectly by selective forces.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1976)105<620:GVICSO>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1976

数据来源: Taylor

摘要:

A school of largemouth bass (Micropterus salmoides) fry was observed and a sample of fry collected for stomach content analysis at 3-hour intervals throughout a 24-hour period. During most of the day, the location of the school changed little, and the fry fed continuously on limnetic zooplankters. The fry did not feed at night, but remained inactive and closely aggregated in one location.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1976)105<624:DAAFOS>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1976

数据来源: Taylor